Warning that ties with Washington could be gridlocked for a long time, Russian President Vladimir Putin said 755 US diplomats must leave Russia.
The order is a response to new American sanctions passed by the US Congress.
The Russian foreign ministry had earlier demanded Washington cut its diplomatic presence in Russia by September to 455 — the same number Moscow has in the US.
"More than a thousand people were working and are still working" at the US embassy and consulates, Putin said in an interview with Rossia-24 television.
"755 people must stop their activities in Russia."
Vice President Mike Pence said Monday Moscow's demand to cut American diplomatic staff will not lessen the US commitment to its allies.
"We hope for better days, for better relations with Russia but recent diplomatic action taken by Moscow will not deter the commitment of the United States of America to our security, the security of our allies and the security of freedom loving nations around the world," Pence said in Estonia after meeting with the leaders of the three Baltic states.
Putin's spokesman Dmitry Peskov on Monday insisted that any hopes of mending Russia-US ties rest on "curing the worsening political schizophrenia" in Washington, but admitted the two sides appeared "far away" from any improvement.
Putin added that an upturn in Russia's relations with Washington could not be expected "any time soon."
"We have waited long enough, hoping that the situation would perhaps change for the better," he said.
On Thursday, the US Senate overwhelmingly approved a bill to toughen sanctions on Russia for allegedly meddling in the 2016 US presidential election and for its annexation of Crimea in 2014.
Iran and North Korea are also targeted in the sanctions bill.
The law now goes to President Donald Trump who had made an improvement in ties with Russia a plank of his election campaign.
Moscow on Friday ordered the US to slash its number of diplomats in Russia to 455 and froze two embassy compounds — a Moscow summer house and a storage facility in the city — from August 1.
In December, the then US president Barack Obama ordered out 35 Russian diplomats and closed down two embassy summer houses that Washington said were being used by Moscow for espionage.